Existing sanding blocks typically have only one sanding surface. Often, the block configuration is not conducive to holding the abrasive material, e.g. sandpaper, without slippage or sagging during the sanding operation. Some conventional sanding blocks employ adhesive or a locking mechanism to hold the sandpaper to the sanding block, increasing manufacturing cost and requiring more preparation or setup time.
Existing sandpaper blocks frequently have additional shortcomings. For Example, tensioning the abrasive sheet is required to preclude the sheet from wrinkling or slippage during use. With currently available sanding blocks, especially single-piece sanding blocks, it is often difficult to load the abrasive sheet and secure it tightly to the block. If the abrasive sheet is not tight, it can wrinkle or tear. Loose or torn sandpaper may cause uneven sanding or possible damage to the work surface. Typically, both ends of the abrasive sheet must be installed on the sanding block simultaneously, which can require considerable dexterity and practice.
Despite the development of a variety of motorized sanding devices, there has always remained a continuing need for handheld sanding blocks. Over the years, a wide variety of sanding blocks have arisen. For example, U.S. Pat. No. 2,765,593 issued to Salmon et al. discloses a SANDING BLOCK consisting of a single piece with slits at the ends to hold the ends of the sandpaper strip. The slits serve to divide the ends of the body into an upper portion and a lower portion. The upper portion is flexible and can be bent upwardly to insert the ends of the sandpaper strip. A combination of matching recesses and ridges within the slits are employed to further grip the ends of the sandpaper strip. This configuration requires that the user bend both the upper portions upwardly while inserting both ends of the sandpaper sheet tightly, and then immediately pressing the upward and lower portions together. The device relies on the combination of recesses and matching ridges, along with hand pressure, to hold the ends of the sandpaper sheet in place, but continuous hand pressure is required to maintain the upper and lower portions together to secure the sandpaper. Whenever the user discontinues the sanding operation and removes his hand, the upper and lower end portions can separate sufficiently to release the grip on the ends of the sandpaper. Another drawback is that a considerable length of the sandpaper sheet is utilized for gripping the ends of the sheet.
Another example of a sanding block having slits at each end to hold the sandpaper strip is U.S. Pat. No. 6,062,966 issued to Ali et al. that discloses a SANDING BLOCK wherein a flexible intermediate portion allows the end portions above the slits to be bent upwardly to install the ends of a sandpaper sheet. To further aid in securing the sandpaper sheet, the top surface of the end portions, below the slits have at least one nail-like retention protrusion. The disadvantage of this arrangement is that it is rather complex and thus costly to manufacture. Another shortcoming is that in order to load the sandpaper sheet, the user must bend upwardly the tops of the end portions in order to insert both ends of the sandpaper sheet. Then the user must immediately press down on the upper portions of the ends in order to ensure that the retention protrusions have punctured the ends of the sheet. This requires a combination of dexterity and some practice.